"Memento," directed by 30-year-old British director Christopher Nolan, is the kind of movie that's bound to be talked about, debated and eviscerated far more than it's understood.

It's the story of a man, played by Australian actor Guy Pearce, whose short- term memory is destroyed when his wife is killed. After the tragedy Leonard Shelby compensates by taking Polaroids, making notes to himself and tattooing reminders on his body -- anything to reorganize his shattered life and avenge his wife's death.

It's not amnesia, he explains, but anterograde memory loss -- the inability to make new memories. Everything until the accident is relatively intact; everything that has happened since tends to vanish.

Nolan based "Memento" on a short story by his brother, Jonathan Nolan, who told it to him during a cross-country road trip. He sets it in Los Angeles -- the tawdry L.A., not the glamorous one -- and uses the story as a springboard to various themes: the relativity of truth, the unreliability of memory and the existential loneliness of a man who constantly feels "like I just woke up."

That's a weighty agenda all by itself, but Nolan adds another layer by telling Leonard's story in reverse. He opens the film with a Polaroid of a murdered man and during the opening credits lets that image fade to nothing instead of materializing.

A murder is then revealed (or cloaked?) and each scene that follows clicks backward in time, ending roughly where the previous one began. Shady L.A. characters, played by Carrie-Anne Moss, Joe Pantoliano and Mark Boone Junior, will enter Leonard's world, appearing friendly one moment and reeking of malice in another.

"Memento" is told from Leonard's fractured perspective, so it's hard to follow -- intentionally so. Like "The Sixth Sense," which also played with notions of time and perception, it's designed to challenge and confound us.

Like "The Sixth Sense," it begs for repeated viewings and gives us (what seems to be) a surprise ending. I've seen it twice now, and I'm still not sure exactly what happens. And I'm wondering: Will anyone?

Nolan's only prior directing credit was "Following" (1998), a little-seen thriller about a would-be writer who escapes his loneliness by following strangers. His next movie, which, judging by its title, would seem to follow a similar thread of ambiguity and identity-seeking, is called "Insomnia."

Nolan may be too clever by half -- witness his fondness for red herrings -- but he has a strong command of the medium and holds our interest with "Memento. " He keeps us grasping for clues and creates a sense of Los Angeles -- again, from Leonard's perspective -- as a bleak, lonely netherworld where people never wake up or come fully into focus.

He's also drawn a tense, passionate performance from Pearce as the emotionally stranded Leonard. Pearce, an acting chameleon, looks nothing like he did in "The Adventures of Priscilla, Queen of the Desert," when he played a bratty drag queen, or "L.A. Confidential," which refigured him as a straight- arrow L.A. cop.

Lean and wiry, his hair dyed blond and worn spiky, Pearce plays Leonard on a note of unbroken frenzy -- like a man whose mind is derailed and who is rushing to get it back on track and moving forward.

Pearce is too scrupulous an actor to plead for an audience's sympathy, and yet there's something in Leonard's lonely search -- his wish to turn the fragments of his life into something whole -- that touches and resembles any one of us.